4 THE GEOLOGICAL EVIDENCES 



evolution is the supposition that if all organic forms 

 are mere derivatives of one another, no matter how 

 unlike they may be, it follows that they occupy a 

 serial position with reference to each other; in other 

 words, it is conceived that if all the connecting forms 

 were discovered, they would build up a continuous 

 organic chain. Nothing could be further from 

 the truth ; evolution recognizes modification in the 

 most divergent directions, and the tree of life that 

 it restores is not a straight stem growing from a 

 continuous apical bud, but a stem, or possibly even 

 a limited number of stems, branching in varying 

 directions. The bird, which, in our conception of 

 structural organization, stands intermediate in rank 

 between the reptile and mammal, appears to be a 

 descendant of the former, the reptile, but the 

 mammal, which immediately follows the bird, has 

 little or no direct connection with it. One line 

 or the other is a side line, and there can be no 

 connection between the two except at their points 

 of divergence. 



Granting the truth of the doctrine of evolution, 



